Hours timer with display - Options needed

[ADWSystems]

I need to incorporate (buy or build) a timer that will display up to 19.9 hours. I have the option of an open collector or relay input to run the timer. The use of a microcontroller is out. They are debating on the use of a PLD (16v8 or 22v10 type stuff might be all I can convince them of). So right now it the only choice I have is discrete chips.

I was thinking of a 555 with running into some sort of high bit count timer (I've seen a 14 bit ripple counter) then into three decade counters. I then need a way to convert from decade to 7 digit display. I'm stuck on this part. Or buy a resettable hours timer, but I haven't found one (inexpensively) yet.

What are your thoughts?

 

[KeepItSimpleStupid]

Check out: **broken link removed**

and Red Lion Controls

 

[ADWSystems]

The panasonic one might not be too bad at $45. The Red Lion versions are $400+ based one a very quick internet price search.

 

[Reloadron]

If you want to go simple these may work for you or a Google of Hour Meter will bring up countless hits. I can buy one cheaper than build one. Red Lion as KISS mentions also makes a good line of elapsed time meters.

Damn, my link sucks. Just follow the link and type in Hour Meter in the search box on the left. Also note that some are resetable and some are not. I believe you want a resettable flavor.

Ron

 

[ADWSystems]

Sorry Reloadron, but I did not see any resetable ones based on the description of each item.

Any thoughts on converting from decade to 7-seg display?

 

[ericgibbs]

Sorry Reloadron, but I did not see any resetable ones based on the description of each item.

Any thoughts on converting from decade to 7-seg display?

hi,
Look at this link for simple counters.
https://www.electro-tech-online.com...asic-3-digit-led-decade-up-down-counter1.html

 

[Reloadron]

If you note the keys ‡Resettable for example at the bottom of the page. There are plenty of resettable versions. Note the symbols and read the sections. As to building one you would use a counter with a BCD output (not decimal like the 4017 for example but BCD like the 4510) then drive a BCD to 7 segment decoder chip. There are also other chips that would do this including triple decade counters in a single package. However, there are ready off the shelf solutions that cost less than building it. I use 120 VAC versions on pumps all the time so we know the runtime on the pumps. I also like the McMaster Carr part number 17045T81 as it provides total time and a resetable interval. What exactly is the application?

Ron

 

[ADWSystems]

I wonder how many circuits have been built when a single chip exists to do the job. I didn't find or know the CD4510 existed. We have a supply of 7447 BCD-7 Seg drivers and LED displays.

 

[Reloadron]

For me most of the time it is easier to buy an off the shelf solution if one is available. Well not just easier but cost effective. This is especially true of complex control projects. Unless what I have a need for is unique then it is off the shelf.

Anyway, there are a variety of decade counters that afford a BCD output. The 74192 and 74193 come to mind. There are also some nice three digit versions in CMOS family which are nice when you need 3 or more digit displays. The Motorola MC14553 chip comes to mind. I have no clue if it is still around as I used it maybe 3 decades ago.

Ron

 

[ADWSystems]

That has always been my biggest question...how do you find out this stuff is available? I had no idea. Since I have to build the front end, either the 4510 for the 14553 with the 7447s make an easy back end.

 

[Boncuk]

That has always been my biggest question...how do you find out this stuff is available? I had no idea. Since I have to build the front end, either the 4510 for the 14553 with the 7447s make an easy back end.

Hi,

to find out if and where stuff is available use **broken link removed**

Findchips will provide a list of vendors including prices for the items.

Boncuk

 

[ADWSystems]

Though the website appears to be a great resource; the question is more conceptual than that. I would not have thought to ask if there was a BCD counter. This is a more obvious chip to look for, others I have run across after the fact were not so easy.

 

[KeepItSimpleStupid]

How's this for a lab: https://www.electro-tech-online.com/custompdfs/2011/06/Lab7.pdf

 

[ADWSystems]

And you've done it again, I looked for a chip like the 14511 but didn't find one. I was planning on using three 7447s.

Question on the 14511, I don't recall but I don't think the displays I have on hand are multiplexed, but I believe they have 3 separate commons. I should be able to tie each of the 3 segments together to the 14511 and the common to the 14511 and this should work, correct?

 

[Reloadron]

If you look back to the data sheet for the triple decade counter I linked to it was the MC14553 I linked to and take a look at page 6 they show the configuration. Take note of the 3 counter outputs labeled DS1, DS2 and DS3. Display 1, Display 2 and Display 3. These signals strobe the displays so that when data for each of the 3 counters is present at the BCD output the correct display is turned on. The displays are strobed so the switching is not visible to the human eye. This allows a single display driver to be used with in this case 3 displays. Note how the displays are in what amounts to parallel.

Ron

 

[ADWSystems]

I could use some assistance with the display driver stage. We apparently have a stock of 3 digit displays but they are common anode. We have neither the 14511 from the 'lab' nor the 14543 from the 15453 datasheet, but we do have some 74LS247s. I have a question about each chip:

14511: Appears to be primarily designed for common cathode displays. For our common anode display, it would require a transistor per segment. Correct?

14543: Appears to be able to drive either common cathode or anode displays, but for common anode displays it cannot sink more than 2.25ma per output. Am I reading this correctly?

74LS247: Can this chip be used in place of the 14543 as shown in the 14553 datasheet on page 6 or the 14511 in the 'lab'?

 

[Reloadron]

The 74LS (Low Power Shottky) 247 is the same as a 7447 but a low power version. It is a TTL family logic chip. It is designed to drive 7 segment common anode displays. The 14543 is designed for liquid crystal type displays. If you have common anode 7 segment LED displays the 74247 will drive them. The chips used in the posted links and circuits are literally a few bucks each. This is getting more complicated than it needs to be. We haven't even gotten into the clock yet. I wish you the best with this project.

Ron

 

[ADWSystems]

I don't think this is too complicated yet still only two chips plus the display (yeah, and all the ancillary resistors, etc.). For the timer, I'll be running a 555 at 22.75Hz through a CD4020 with bit 14 sent to the 14553 clock input. I'm debating if the 22.75 is too slow, if it is then I'll up the speed and piggy back another 4020. I looked for a counter that would divide the frequency down more than 14 bits, but didn't see one.

 

[Reloadron]

What frequency clock do you want? This is a popular route to take
for a 1 second clock. The ***** is that using a 555 as the heart sucks as the 555 drifts all over and in general if you want any form of accurate time go with a crystal design.

Ron

 

[ADWSystems]

I hadn't realized the 555 drifts. Then again I've never tried to use one as a timer.

I try keep my questions concise by omitting other aspects of the deisn that people may want to comment on that aren't really the focus of my original question, thus I never get my question answered. But as we're past the point and I have some answers and info to move forward. Here is some more of the design.

What I really need is a small pulse every .1 hours to increment the 14553.

Originally I was going to gate the 555 output to stop the timer, but now I realize the counter stage will need to be reset when the next test starts so I have to rethink this stage. So gating the clock is irrelevent and I could use the 4060 instead of the 555 as you linked. You wouldn't happen to have a link for cascading a 4060 and 4020 would you?

Plus I have the latch function available on the 14553 so I can look to incorporate that instead or as well.